In general, a photographic light-sensitive material comprises a silver halide photographic emulsion layer coated directly or via a subbing layer on either or both sides of a support such as cellulose acetate, polyethylene terephthalate, paper and paper laminated with polyethylene terephthalate on both sides thereof, and optionally an interlayer, a protective layer, a filter layer, an antistatic layer, an antihalation layer, etc. coated thereon in various combination. These layers normally comprise a hydrophilic binder such as gelatin as a constituent. An example of the photographic light-sensitive material comprising a photographic emulsion layer provided on both sides of a support is a direct X-ray film. Most photographic light-sensitive materials comprise a photographic emulsion layer provided on only one side of a support. Accordingly, the latter has an uncoated surface, i.e., a surface of the support. This is normally called "back face" of the photographic light-sensitive material in the art.
A photographic light-sensitive material is often liable to serious adverse effects produced by contact friction with the portion of various apparatus, machines and camera with which it comes in contact or contaminants such as dust and lint during production step such as coating, drying and processing or handling such as winding, rewinding and conveyance upon picture taking, development, printing, projection, etc. In particular, the back face has more opportunity to come into direct contact with various apparatus and machines and is liable to damage such as scratch, deterioration of the drivability of the light-sensitive material in camera or other machines, and generation of film dust. Such a damage as scratch appears on the image during printing or projection and thus causes serious defects in the practical use. Further, due to the recent expansion of the use or processing of photographic light-sensitive materials, e.g., high speed coating, rapid photographing and rapid processing, and the diversification of the working atmosphere as in a high humidity and temperature atmosphere, the photographic light-sensitive materials are subject to harsher usage and thus are more liable to damage and drivability drop than ever. Thus, a photographic light-sensitive material whose surface exhibits a high slipperiness and scratch resistance enough to withstand under such severe conditions has been desired.
As a method for improving the slipperiness and scratch resistance of the back face of a photographic light-sensitive material, there has heretofore been used a method which comprises providing a surface layer containing a slip agent. Known examples of such a slip agent include polyorganosiloxanes as disclosed in JP-B-53-292 (The term "JP-B" as used herein means an "examined Japanese patent publication"), higher aliphatic amides as disclosed in U.S. Pat. No. 4,275,146, higher aliphatic esters (esters of C.sub.10-24 aliphatic acid with C.sub.10-24 alcohol) as disclosed in JP-B-58-33541, British Patent 927,446, JP-A-55-126238, and JP-A-58-90633 (The term "JP-A" as used herein means an "unexamined published Japanese patent application"), metallic salts of higher aliphatic acid as disclosed in U.S. Pat. No. 3,933,516, and polyester compounds made of dicarboxylic acid having up to 10 carbon atoms and aliphatic or cyclic aliphatic diol as disclosed in JP-A-51-37217.
By applying such a slip agent to the surface layer, the slipperiness and scratch resistance of the photographic light-sensitive material can be improved. However, the application of such a slip agent to a photographic light-sensitive material causes some troubles. Firstly, for example, when a silicone is applied to the back layer, it migrates to the surface of the support on which a photographic emulsion is coated, drastically deteriorating the coatability (e.g., attraction, wettability) of the support with the photographic emulsion. This causes uneven coating of emulsion. Even if the emulsion can be coated on the support, the migrated slip agent causes poor adhesion of the emulsion to the support. Thus, the migration of the slip agent to the side of the support on which the emulsion is coated (hereinafter referred to as "undercoating side") after the coating of the slip agent causes some troubles.
These troubles can be significantly solved by the use of a higher aliphatic acid and its derivatives. However, another problem is that the use of a higher aliphatic acid, higher aliphatic amide, metallic salt of higher aliphatic acid or the like causes bleeding of the slip agent during coating or with time to produce a white powder or elution or falling of the slip agent, impairing the effects of the slip agent or contaminating the processing solution.
It has been found that these troubles can be significantly solved by the use of a polyvalent alcohol ester of higher aliphatic acid, higher alcohol ester of straight-chain or branched higher aliphatic acid, higher aliphatic dicarboxylic acid, diester of diol, oligoester compound containing a higher aliphatic acid, or the like.
The surface of the back layer on the support is normally provided with a binder layer for the purpose of protecting the underlying layer or providing a matting layer or AS layer. Accordingly, the foregoing slip agent is preferably incorporated in the binder to minimize the number of layers to be coated. If the foregoing slip agent is used with a binder, it is incorporated therein in the form of solution or dispersion. In this case, if the slip agent is applied in the form of solution, some troubles occur. For example, the slip agent is not dissolved in the coating solution. Further, the slip agent diffuses into layers under the slip layer on which it is coated, or, if the support itself swells with the coating solvent, it further diffuses into lower layers, reducing the amount of the slip agent occurring in the surface and thus deteriorating the slipperiness thereof. This also requires a large amount of a slip agent. Further, if the slip agent is applied in the form of dispersion, it causes some troubles. For example, the haze of the material is increased. The slipperiness and scratch resistance of the material are deteriorated as well. The dispersion stability of the slip agent in the coating solution is not sufficient, causing the slip agent to be agglomerated or sedimented during or after coating. This makes impossible to obtain satisfactory properties.